In microelectronics photolithography, photomasks are employed to replicate by exposing a pattern on a semiconductor wafer. When the microelectronics fabrication processes progressing into the sub-half-micron scales, the demand of higher performance photolithographic techniques has been increased. A recent trend in microelectronics photolithography has been the use of electromagnetic energies with extremely short wavelengths, or instance, in the UV wavelengths, in the X-rays, etc.
In microelectronics photolithography for replicating patterns, it may be necessary to repair the photomask since the mask fabrication process cannot produce defect-free masks at high yield. On binary intensity masks (BIM), there are two types of repair, i.e. filling pinhole defects shown in FIGS. 1A and 1B, and removing opaque defects shown in FIGS. 2A and 2B.
More recently, the technique of phase-shifting mask has been developed to improve the resolution of optical imaging systems. FIGS. 3A, 3B and 3C illustrate problems and results in repairing phase-shifting masks (PSM), wherein phase errors in critical areas have to be repaired in addition to the intensity defects. It is difficult to add or to remove phase shifting materials precisely in depth or refractive index to restore the desired phase relationship.
In another recently developed photolithography technology of extreme UV (EUV) lithography, the mask repair task is even more difficult. This is shown in FIGS. 4A, 4B and 4C. Since the EUV masks are reflective in nature, the mask blank is coated with more than 40 pairs of interference thin film materials to make it reflective. An absorber layer is coated on top of the multi-layer to be selectively removed according to the desired pattern on the mask. Even though repair of the absorber is similar to repairing the absorber pattern in a transmissive BIM, repairing any defect on the multi-layer reflecting areas is extremely difficult. Presently, there is no known method for adding or removing all the layers to the thickness specification, let alone the difficulty of making the repair seamless.
U.S. Pat. No. 6,031,598 to Tichenor et al, discloses an EUV replication system which includes a light source means, a condenser means, a mask means, an imaging lens means, and wafer means as shown in FIG. 3. However, Tichenor et al does not disclose any provision for repairing of the resist latent image itself.
U.S. Pat. No. 5,978,441 to Early, discloses an EUV mask making method by depositing multiple layers on the mask blanket. However, Early does not disclose any method for repairing a mask substrate.
U.S. Pat. No. 5,935,737 to Yan, discloses an EUV mask repair on a mask substrate but not on the resist latent image.
It is therefore an object of the present invention to provide a method for repairing resist latent image on a wafer that does not have the drawbacks or shortcomings of the conventional method .
It is another object of the present invention to provide a method for repairing resist latent image on a wafer in an image scanner that is equipped with a primary imaging column and a supplemental imaging column.
It is a further object of the present invention to provide a method for repairing resist latent image on a wafer wherein the exposure on a first wafer and the repair on a second wafer can be conducted simultaneously in the same vacuum chamber.
It is another further object of the present invention to provide a method for repairing resist latent image on a wafer by utilizing a primary imaging column of EUV imaging optics and a supplemental imaging column of E-beam imaging optics that operate in the same vacuum chamber.
It is still another object of the present invention to provide a method for repairing resist latent image by irradiating an energy beam on a resist defect wherein the energy beam may be an E-beam, an ion-beam or an optical beam.
It is yet another object of the present invention to provide an apparatus for repairing a resist latent image on a wafer which incorporates a primary imaging column and a secondary imaging column.
It is still another further object of the present invention to provide an apparatus for repairing a resist latent image on a wafer which incorporates a primary imaging column and a secondary imaging column that operates in the same vacuum chamber.
It is yet another further object of the present invention to provide an apparatus for repairing a resist latent image on a wafer incorporating a first wafer chucking means and a second wafer chucking means capable of moving the wafer in an X-Y direction.